Pro-Russia supporters look at fireworks as they gather outside the regional state building in the eastern Ukrainian city of Donetsk on May 12. / Genya Savilov, AFP/Getty Images

by Luigi Serenelli, Special for USA TODAY

by Luigi Serenelli, Special for USA TODAY

Militants ambushed a convoy of Ukraine soldiers Tuesday, killing six soldiers as both sides had been moving toward possible peace talks in Kiev.

German Foreign Minister Frank-Walter Steinmeier was in Ukraine to try to broker talks between the central government and pro-Russia separatists who held a referendum to join Russia.

Prime Minister Arseniy Yatsenyuk said Ukraine has drawn up its own plan for ending the crisis and does not need European proposals.

Ukrainian forces have been trying to put down the armed insurgents in eastern Ukraine, where 40,000 Russian troops are massed on the border in preparation for a possible invasion.

On Tuesday the Defense Ministry said six Ukrainian soldiers were killed by militants after the separatist leader in Luhansk, one of the regions that declared independence, was shot and wounded.

Russia has said Ukraine should respect the results of a weekend referendum run by the militants who said nearly 90% of people in the region voted for autonomy from the Ukrainian government. Russian President Vladimir Putin says he has the authority to invade to protect the ethnic Russians who make up the militancy.

European analysts say there is no need for Russia to invade eastern Ukraine now that it has gained ultimate authority over much of the country by its takeover of Crimea and declarations of independence in the pro-Russian east.

"The referendum actually advantages Russia," said Keir Giles, analyst at Chatham House's International Security and Russia and Eurasia Program London.

"They do not need to have physical control of these regions to achieve their objective for the Ukraine, which is always has been to render Ukraine ungovernable."

Russia has called for the international community to respect the decision of the people of the Donetsk and Luhansk regions and is calling for a "practical implementation of the outcome of the referendum in a civilized manner, without any repeat of violence and through dialogue," the Kremlin said.

The referendums follow one held in Crimea in mid-March by pro-Russian separatists there that resulted in a Russian military invasion and annexation of the Black Sea peninsula. Ukraine says the votes were rigged and the United States termed them illegal.

Many have wondered if the latest votes are a pretext for Russian takeovers in the eastern Ukrainian regions.

"Russia annexed Crimea very quickly â?? we don't know if would be the same in Donetsk at all," said Andrew Wilson, senior policy fellow at the European Council on Foreign Relations in London, referring to a province in eastern Ukraine held captive by militants.

"In bigger-picture terms Russia can better control the guys in Crimea â?? they are real puppets. It is pretty unlikely that Russia would want to control south and eastern part of Ukraine as a whole, and it is pretty difficult to take only Donetsk."

Some analysts say if Russia ultimately accepts the move for independence, the provinces could end up as a puppet state.

"If Russia accepts the independence, we will have definitely a situation like in South Ossetia or Abkhazia or Transnistria, an independent state supported by Russia and in particular by the Russian military," said Liana Fix, an analyst specializing on the region at the German Council of Foreign Relations.

Meanwhile, Putin is pretending to lose control of the situation in the east just as he did when rebels in Donetsk kidnapped officials from the Organization for the Co-operation and Security in Europe, added Fix. That is to show he can present the face of a "good guy" to the world.

But it has been largely pro-Russian separatists who for the past few weeks have stormed and occupied official buildings in eastern Ukraine, prompting the Ukrainian government to launch military operations to push them out.

"The situation is not as bad as it could yet be - it could go either way - but (it getting) even worse is more likely," Wilson said.